1. Technical Field
The present invention relates to the field of sound absorbing cotton, and more specifically, to a high sound absorption coefficient expanded PTFE composite fiber cotton.
2. Description of Related Art
Although automobiles have a very beautiful shape by virtue of streamline design and smooth connection of curved surfaces, noise pollution of automobiles is still hard to decrease. Sound is produced by the to-and-fro movement of air molecules, which is caused by vibration of a body surface and this movement causes change in the air density between local compression and expansion and propagation thereof. Noise produced by a moving automobile will affect the degree of comfort persons in it feel, and makes people feel tired and sleepy more easily, which tends to cause an accident; the method for reducing noise pollution includes absorption, shielding or blocking.
Some vehicles produced abroad such as Ford, GM and VW have used new sound-absorbing materials made of fibrous composite non-woven fabric or aluminum film. The energy of sound is attenuated as noise passes through the porous materials of micro-fine fiber and causes friction. By reducing the propagation of sound energy through the reflected echo waves of composite non-woven fabric or aluminum film, sound absorption materials with the micro-fine fiber technology convert most noise energy into heat, substantially reducing the noise in automobiles. Some vehicles produced nationally also begin to use the noise reduction technology, but sound absorbing products for automobiles have to be imported and the market of sound absorbing cottons has been monopolized by foreign enterprises.